Voltage regulation



26, 195 B. STEVENS VOLTAGE REGULATION 2 Sl-lEETS-Sl-IEET 1 Filed Jan. 21, 1949 Quin BA kbok b0 INPUT VOLTAGE Nu vRq k boCbO INPUT VOLTAGE INVENTOR B. E. STEVENS ATTORNEY Patented Aug. 26, 1.952

QLIIZAGE R GULAT IIQN Bruce E; Stevens, Cluster, NijJ., assignor to Bell:

Telephone Laboratories,

Incorporated, New

York; N. Y'., a corporation of-NewYork mgnlicatic lanuary 21, 9. 9, S ria .No,.7Z,9.l

20 Claims. 11

This. invention. relates. to, current. supply. an.- Daratus and particularly to apparatus for. sup-- p yin current. from a natins urrent s ply QUrcetQaJOad and for maintaining; hemed voltage substantially constant,

.enlobjectof the. inventiohuis to, provideah. improved. voltag -r u ated.- alterhat n rcurrent supply apparatus...

The. currentsupply appa atus; oi; the present invention is, in some. respec fi simllar to, that. dis,- closedin: my United states Hatent N}. 2,333, 11. granted November-2,1943 hutis anlmprovement thereover. Some advantages, of the... volta e.- re u a cd. urrent s pply apparatus; oi. the pre ent invention are, relatively low cost. a high voltamp r -r t ng relative tosize, low harmonic. 0. 1- tent oioutput current... a. high.,lnputp weriactcr h h efiiciency, relative stabili y with,v frequency and temperature changeand low heat generation.

In. a preferredv embodiment of h in nti n, thereis derived from an. alt rnating current sup! ply sourceanalternatlng voltage whichis smaller than the voltage of the. supply-source and which varies. in respon e o supply vol.tag,ev ch nges. the percentage variation of; thesderived volta qbeing larger than the percentage variatipn of. the supply line volta e nd. the pha e. of; he deriv d voltage varying'vvith respect, to the, phase of the supply voltage. Afloltage; equal to the. vector sum of th supply voltage, r a, v l ag propertional to the supply voltage. and the derived voltage is impressedupona load to maintain the load voltage substantially constant irrespective of voltage'chan es of: the source. 7 Pref rably t derived. voltage is 8.0 chosen that it is out of, phasewith, respect to the. line; voltag y less than. 90 de rees, the derived volta e decrea i as t line voltage increases,. so that the lfesultantof the line volta e. and. thederived vo age. i lar r than either. of, the. component voltages. If desired, the derived. voltage having the decreasing characteristic. as, the linevoltage is increased may he of larger magnitude. than. the. line. voltage and change at a smaller rate-- In some. ases oreover, it may be. desirable to employ a derived voltage. which is out" oi phasewith. respec to the line. voltage by a, phase angle, between 9.0 degrees and 1.80 degrees, the derived, voltage. increasing as. the line voltage increases. I

In. order that the load voltage. mayh ve a. c.- sired root-mean-squarel value equal -to, larger than or smaller than the nominal rooftmeanquare. value of the line. volta e, there may be included in the. load, circuit, a, second voltage. derived from the supply source which is relatively con tant r. whichvariesr latiye y slowly. the source. volt e: hansesthe. fl st de ived v lt es be n adiustedtc om h fo theu riat of; the. s cond. d rived vqltase. as. ell. a er the l nev ta e. variations .0. hat.thelcadiv tagc r mains ub a t al y ons an I a spe ficemhodimcnt or theln eht ohherei shown. and escrihed o t e nur csect 1 tratiqn, the apparatus nrqyi cd cr h ainin the de ived. vo ta e, r. oltaeesw ich s. 0r wh ch a e nserie wit the. sup ly vol age our an the load comprises a. first and: a second. ndu anc device, each having acoreof; magnetic, material and a. winding. h reon). and a condense T winding. of the. fi t.v d vice. the, condenser and a portion of the winding of the second devicev are c nnec ed in. t at Qrder 1 .61 W th-e h. Oth r and with an alternatin -.curr ent supply source tov for a r e f rro-r sona tc u t rati abovethe jumping point of its characteristic current-voltage curve so that the capacitive re actance of the circuitis larger than its ind ctive reactance, A portion of} the winding of the first device and the remaining portion of the wind n f h se nd dev c a e ne te n a se cuit wh ch iQ onv n en e. ma be called. a control, circn lt. in series with each other a with the su ply source- Th cu r nts i a u ts, r spectiv ly, cause t be s p in the core of said first. device magnetomotive forces which are opposing an t e core f ai s 0nd device, magnetomotive forces. which areaid ing. The magnetic flux in the core. in which the aiding magnetomotive forces are. set. up is suffic ht ma tude. to. ma n ti the core t a po nt above t e knee of t ma eti atio curve and any effective air-gap in the ma netic circuit should be held to a minimum. The other ore ne o be o erated abo e. e. n o the magnetization curve The. magnetolnotive force set up in each core due. to. the. current in the ferrosresonant circuit rises relatively slowly or eve de e s a t e. supply sou ol a ncreases while the, magnetomotive. force set up in each core due to the. current. in the control circuit rises relatively rapidly as. the. supply voltage increases. The magnetornotive force due to the current in the ferro-resonantcircuit is preferably larger than that. due to. the. current in the control circuit for bothinductance devices although the magnetomotive force- .due to the current in the'ferrorresonant. circuit may be smaller in the case of the first inductance device. The load circuit comprises. i ser the supply o ta e source, a portion of the winding of the first inductance device and the load and it may also include a portion of the winding of the second inductance device. When the supply voltage rises, for example, the voltage across the portion of the winding of the first inductance device de-- creases sufiiciently and changes in phase in response to the increase of the supply voltage to cause the load voltage to be maintained substantially constant.

In some cases it may be desirable to insulate the load or output circuit from the current supply source. For this purpose each inductance device may be provided with two windings which are insulated from each other. A winding of the first device and a winding of the second device are connected in series to the alternating-current supply source. The second winding of thefirst device, the condenser and the second winding of the second device are connected in series to form a series ferro-resonant circuit operating above the jumping point of its characteristic currentvoltage curve, a voltage being induced into the ferro-resonant circuit due to the alternating current inthe first Winding of each inductance device. The load circuit is connected across a part of the ferroresonant, circuit comprising a portion of each of the windings in the ferroresonant circuit and the condenser.

If desired, the two inductance devices may be combined by mounting, the winding or windings of the one inductance device on one of the outer legs and the winding or windings of the other inductance device on the other outer leg of a three legged core structure. i The invention will now be described with reference to the accompanying drawing in which: 7 Figs. 1, 2, 3, 4, 10 and 11 are diagrams to which reference will be made in explaining the operation of the invention;

Fig. 5 is a schematic view of an alternatingcurrent voltage regulator embodying the invention; and v Figs. 6, 7, 8, 9 and 12.are schem atic views of modifications of the voltageregulatondepicted inFig.5

."Referring to the drawing," there is shown in Fig. 1 a circuit arrangement for supplying alternating current from a supply source I 5 to a load I6 to obtain an output or loadvoltage which decreases as the input or line voltage increases, as

shown by the curve of Fig. 2; The circuit arrangement comprises a first inductance device having windings I1, I8 and I9 wound on a magnetic core 20 forming a closed magnetic path,

a second inductance device having windings 2| and 22 on a magnetic core 23.forming a closed magnetic path and a condenser 24. Winding 22, condenser 24 and winding I8 are connected in series to the alternating-current supply source I5 to form a ferro-resonant circuit operating above the jumping point'of its characteristic current- Fig. 1 is similar in design to that shown in Fig. 3 of the United States Patent No. 2,297,672, granted to me September 29, 1942..

The magnetomotive forces setup in the magis connected to the winding I9. .The circuit of netic circuit of core 23 bythe currents in wind- 4 ing I8 are greater than the ampere turns of winding II. Since the current in the ferroresonant circuit including winding I8 rises relatively slowly, or even decreases, in response to an increasing line voltage and since the current in winding [1 increases relatively rapidly in response to a line voltage increase, the resultant flux in the core 20 decreases in response to an increase of; line ,voltage,,.and vice versa. Therefore, the load voltage decreases in response to an increase of line voltage and vice versa, as shown in Fig. 2. The rate of decrease of the load voltage can-be greater than the rate of increase of the line voltage.

As the ratio of the ampere turns of winding I3 with respect to the ampere turns of winding II is increased, a point will be reached where an increase of the magnetomotive force due to a current increase in winding I8 will substantially equal the increase of magnetomotive force due to the current increase in winding IT, as the line voltage rises, sojthat the load voltage tends to become constant as the line voltage changes.v

Fig. 3 is like Fig. 1, the corresponding parts having the same designation, except that the ampere turns of winding II are greater than the ampere turns of winding I8. Therefore, the phase of the resultant flux in core 20 is reversed as indicated by the arrow next to the core 2e and the load voltage will increase as the line voltage increases;' and vice versa, as depicted by the curve of Fig. 4. The rate of increase of the load voltage canbe greater thantherate of increase of the line voltage. 1 i e 7 Fig.5 is like Fig. 1 orFig. 3, the corresponding parts bearing. the same designations, with the followingexception, Instead of connecting the load I6 across windingIS, as in Figs. 1 and 3, the load is connected in'a circuit comprising winding I9 and the alternating-current source I5, all in series. As the line voltage changes, the magnitude and phase of the derived voltage across windingIB will also change so that a resultant voltage equal to the vector sum of the, line voltageand the derived voltage, which resultant voltage islimpressed upon the load, remains sub stantially constant. 3' 7' The operation of; -tlie regulator of Fig. 5 may be better understood from a consideration of the vector diagrams ofFigs 10 and 11. Preferably the ampere turns ofwinding I8 are greater than the ampere turns'of Winding I I. In this case the diagram of Fig. 10 is applicable. The current in the ferro-resonantcireuit flowing through condenser24 is designated by the vector I24 extending horizontally toward the right from the origin. The voltage E24 across the condenser lags the current 124 by degrees. The voltage E22 and the voltage EIB across windings 22 and I8, respectively, eachlead the current I24 by less than 90 degrees,the voltage E22 being. larger than the voltage EIB. The line voltage EI 5 which lags the current I24 by about 60 degrees is found by vectorially adding voltages E22, EH8 and E24. The derived voltage EI9 across winding I9 is 0pposed in phase to the voltage El 8'. The line voltage El 5 and the derived voltage El 9 are less than 90 degreesfl'outf'of phase and the vector sum of these voltage components is the voltage E15 which is impressed a cross the load and which remains; jsubstanti "lly constant irrespective of variationsofheli jvoltageEIf In some casesit'may bedesirable to have the diagramof Fig. 11 is applicable. The vectors I24 and E24 are the same in Fig. 11 as in Fig. 10 and the phase of vector I8 is now reversed with respect to its phase in Fig. 10. The line voltage E| in Fig. 11 has the same magnitude as in Fig. but lags the current I24 by somewhat more than 90 degrees. The derived voltage E|9 has about the same magnitude as in Fig. 10. In Fig. 11, the line voltage E|5 and the derived voltage Eli! are more than 90 degrees out of phase with respect to each other so that the vector sum of these voltages, EIB, is less in Fig. 11 than in Fig. 10. However, the load voltage E|6 is maintained substantially constant irrespective of the line voltage variations.

The regulator of Fig. 6 functions like the regulater of Fig. 5 but is simpler and less expensive. it comprises an inductance device comprising a single continuous winding 33 wound on a core 3| forming a closed flux path, a second inductance device comprising a single continuous winding 32 wound on a core 33 forming a closed flux path, and a condenser 39. Each of the coils has taps intermediate the end terminals of the coil. The winding thus comprises two portions 34 and 35 and the winding 32 has three portions 36, 31 and 38. Current from an alternating-current source is supplied through the regulator to a load 4| to maintain the load voltage substantially constant. The ferro-resonant circuit corresponding to the ferro-resonant circuit of Fig. 5 comprises the supply source 43, winding portion 35, condenser 39 and the entire winding 32, all in series. Winding, portion 34 corresponds to winding 2| of Fig. 5 and winding portion 33 corresponds to winding ll of Fig. 5, winding portions 35 and 38 being connected in series to the alternating-i current source 40. There is provided a circuit comprising source 46, winding portions 38 and 3'! and load 4|, all in series. Thus, the derived voltage across portions 31 and 35 of winding 32 and the voltage of the supply source Mlv are added vectorially to produce a resultant substantially constant voltage which is impressed upon the load 4|. The derived voltage corresponds to a voltage across winding IQ of Fig. 5. The vector diagrams of Figs. 10 and 11 thus apply when it is borne in mind that the derived voltage of Fig. 6 corresponds to the voltage across winding I9 of Fig. 5.

Fig. '7 is like Fig. 6, the corresponding parts bearing the same numerals, but is designed to permit a portion 53 or 5| of winding 30 to be included in the load circuit in series with the source 46, a portion of winding 32 and the load 4|. The terminals of load 4|, respectively may be connected to coils 33 and 32 by way or taps 52 and 53 to provide a load voltage having a root-mean-square value greater than the nominal root-mean-square value of the line voltage or by way of taps 54 and 55 to provide a load voltage having a root-mean-square value equal to the nominal root-mean-square value of the line voltage. If desired, moreover, the taps 54 and 55 may be so chosen as to provide a load voltage having a root-mean-square value which is less than the nominal root-mean-square value of the line voltage. These results are obtained when the derived voltage across a portion of winding 32 has a decreasing characteristic as shown in Fig. 2.

In a specific regulating circuit of the type shown in Fig. 7, the nominal voltage of the supply source was 115 volts, 60 cycles, the capacitance of condenser 39 was 7 /2 microfarads, the lower portion of winding 30 which is in the term-resonant circuit had 155 turns, the remaining portion of winding 30 had 250 turns and the winding 32 had 405 turns. The lower'portion of winding 32 which is connected in series with the upper portion of winding 35 to the source 46 had turns, so that the remaining portion of winding 3-2 which is in the ferro-resonant circuit had 285 turns. The portions 50 and 5| of winding 33 each had 50'turns. The portion of Winding 32 betwen the tap 53 and its lower terminal which is connected to a terminal. of source 46- had 1'75 turns and the portion of winding 32 between, tap 55 and its lower terminal had turns. The winding 30 and the winding 32 were wound on the middle legs respectively of two three-legged cores. Each core structure comprised a l /z-inch pile up ofv 0.0.1.4-inch silicon steellaminations. The middle legs. were 1% inches wide and the outer legs. were is inch wide. The length of the mean. magnetic path including the middle leg and one of the outer legs was 8% inches.

Fig. 8 shows a modification of the regulator described above in which the load circuit is insulated from the current supply source. Gurrent is supplied from alternating-current source 60 to a load 6.1 through a regulator comprising two inductance devices and a condenser 62, the one inductance device comprising windings 63 and 64 having a core 65 and the other inductance device comprising windings 66 and 67 having a core 68. The load is connected to windings 64 and 6.! by way of taps 69 and I6, respectively, or by way of taps H and, 12, respectively. when the voltage across windings 63 and 6'! have a decreasing characteristic. Winding 6d, condenser 62 and winding 67 are conductively con ected in series to form a ferro-resonant circuit operating above the jumping point of its characteristic current-voltage curve so that its capaci'tive reactance is greater than its inductive reactance. Windings 63 and 66 are insulated from windings 6:4] and. 6'! and are connected in series. with each other to the supply source 55 as shown.

The regulator of Fig. 8 operates in the same manner as the regulator of Fig. 7 to maintain the load voltage substantially constant irrespective of voltage changes of the, source. This may be better understood from the following analysis. The operation of Fig. 8, would not be changed if the upper terminals of windings 63. and '64, as viewed in the drawing, were conductively connected and if'the lower terminal of winding 63 were conductively connected to a point. of winding 64 between taps 69 and H such that the portion of winding 64 which is connected across winding 63 has the same number of turns as Winding 63. Winding 63 and the portion of winding 64 connected across it would then be equivalent to the portion of winding 36 of Fig. 7 which is connected in series with a portion of winding 32 and the source 49. With this change in Fig. 8, the upper terminal of winding 66 will be conductively connected to the lower terminal of winding 61. Therefore, in the circuit as.modifiei'a ferro-resonant .circuit would comprise a lower portion of winding 64, condenser 62, winding 61, winding 66 and the source 66. The load circuit would comprise source 60,. a small portion. of winding 64 corbetween a terminal of the supply source and a load terminal is added in series with the supply source voltage while in Fig. 8, as modified, the derived voltage across winding 66 and a portion of winding 61 is added in series with the supply source voltage. In Fig. 7 there is also included in the load circuit a voltage across a small portion of winding 30 connected between a terminal of the supply source and a terminal of the load while in Fig. 8, as modified, the voltage across a small portion of winding 64 is included in the load circuit. Y

The regulators of Figs. 5, 6, '7 and 8, employ entirely independent core structures for the windings of the inductance devices, respectively. However, the windings of the devices may be wound on the outer legs, respectively, of a threelegged core structure as shown in Fig. 9. To facilitate comparison with Fig. 6, the corresponding parts in the two figures are designated by the same numerals. As in Fig. 6, winding portion 35, condenser 39 and winding 32 are connected in series to the supply source 40 to form a ferro-resonant circuit operating above the jumping point of its characteristic current-voltage curve. Winding portion 34 and Winding portion 38 are connected in series to the source 40 to form a control circuit. The vector sum of the source voltage and the voltage across winding portions 3'! and 38 is impressed across the load ll. The current in the ferro-resonant circuit and the current in the control circuit cause aiding magnetomotive forcesto be produced in leg 3| of the three-legged core structure and cause opposing magnetomotive forces to be produced in the other outer leg 33. Either of the component magnetomotive forces in leg 33 may be larger than the other.

A modification of the embodiment of the invention of Fig. 8 is shown in Fig. 12, corresponding parts of the two figures being designated by the same numerals. A three-legged core structure is used in Fig. 12, windings B3 and 64 being wound on one of the outer legs 65 of the core structure and windings 66 and 6'! being wound on the other outer leg 68.

What is claimed is:

1. In combination, a first and a second inductance device each comprising a core of magnetic material and a winding thereof, a condenser, a source of alternating current, a load, a first circuit comprising in series in the order named said source, the winding of said first device, said condenser and a portion of the winding of said second device, a second circuit comprising in series said source, a portion of the winding of said first device and a portion of the winding of said second device, and a third circuit comprising in series a portion of the winding of said first device, said condenser, a portion of the winding of said second device and said load.

2. In combination, a condenser, a first and a second winding wound on a first and a second core of magnetic material, respectively, a ferroresonant circuit comprising said condenser and a portion at least of each of said first and second windings, all in series, a second circuit comprising a portion only of said first winding, said condenser, a portion only of said second winding and a load, all in series, and means for supplying alternating current from an alternating-current supply source to said ferro-resonant circuit to cause it to operate above the jumping point of its characteristic current-voltage curve so that its capacitive reactance is greater than its inductive reactance.

3. In combination, a condenser, a first and a second winding wound on a first magnetic core, a third and a fourth winding wound on a second magnetic core, a ferro-resonant circuit comprising said condenser and said second and fourth windings, all in series, means for supplying alternating current from a supply source to said first and third windings, the magnetomotive forces set up in said second core due to the currents in said third and fourth windings, respectively, being in opposition with respect to each other, said ferro-resonant circuit operating above the jumping point of its characteristic current-voltage curve so that its capacitive reactance is greater than its inductive reactance, and a load connected in a circuit comprising a portion only of said second winding, said condenser and a portion only of said fourth winding.

4. In combination, a first, a second, a third and a fourth winding, said first and second windings having a common magnetic core and said third and fourth windings having a common magnetic core, a condenser, a ferro-resonant circuit comprising said condenser and said second and fourth windings, all in series, a load connected in a circuit comprising a portion only of said second winding, said condenser and a portion only of said fourth winding, and means for supplying alternating current from a supply source to said first and third windings in series to cause a current to flow in said ferro-resonant circuit, the currents flowing in said first and second windings, respectively, causing aiding magnetomotive forces to be set up in the common core for said first and second windings, the currents flowing in said second and fourth windings, respectively, causing opposing magnetomotive forces to be set up in the common core for said third and fourth windings, said ferroresonant circuit operating above the jumping point of its characteristic current-voltage curve so that its capacitive reactance is greater than its inductive reactance.

5. In combination, a first, a second, a third and a fourth winding, a first circuit comprising said first and third windings connected to an alternating-current supply source, a condenser, a second circuit insulated from and magnetically coupled to said first circuit, and said second circuit comprising said second and fourth windings and said condenser forming a series ferroresonant circuit operating above the jumping point of its characteristic current-voltage curve so that said ferro-resonant circuit has a capacitive reactance greater than its inductive reactance, and means for connecting a load across a portion of said ferro-resonant circuit.

6. A combination in accordance with claim 5 in which the currents flowing in said first and second windings cause aiding magnetomotive forces to be set up in a magnetic circuit for said first and second windings and in which the currents flowing in said third and fourth windings cause opposing magnetomotive forces to be set up in a magnetic circuit for said third and fourth windings and in which said load is connected in a circuit comprising a portion only of said second winding and a portion only of said fourth winding, said two winding portions and said load all being in series.

'7. In combination, a three-legged core of magnetic material, a first and a secondwinding on the outerlegs, respectively, of said core, a condensen'a circuit comprising a portion only of said first winding, saidcondenser andsaid second winding and a source of alternating current, all in series, a second circuit comprising another portion only of said first winding, aportion only of said second winding and said source, all in series, a load, and a thirdcircuit comprising saidload a portion only of said second winding and said source, the currents flowing in said first and second-circuits, respectively, causing opposing magnetomotive forces to be produced in the leg of said coreupon which said second winding is wound. J V a I f 8,;In combination, a three-leggedcore'ofmagnetic material, a first and a second winding on one of the outer :legs of said core, a third and afourth winding on the other outerleg of the core, a first circuit comprising said first andithird windings and a source ofalternating current. all inseries, a condenser, asecond circuit insulated from said first circuit comprising said second and fourth windings and said condenser 'all in series, and a load circuit connected across a portion of said second circuit which comprises a portion only of said second winding, said condenser and a portion only of said fourth winding.

9. In combination, a first and asecond Winding each for setting'upflux in'acore ofmagnetic material, a ferro-resonant circuit comprising a condenser, a portion at least of each of said windings and a supply source of alternating current all connected in series, said ferro-resonant circuit operating above the jumping point of its characteristic curve so that said ferro-resonant circuit has a capacitive reactance greater than its inductive reactance, a second circuit comprising a portion of each of said windings and said alternating-current source all connected in series, whereby there is set up across a portion at least of said first Winding a derived alternating voltage the root-mean-square value of which decreases in response to an increase of the root-mean-square value of the voltage of said source, and vice versa, a load, and means for impressing across said load a resultant voltage having as components the voltage of said source and said derived voltage.

10. The combination with an alternatingcurrent supply source and a load, of a ferroresonant circuit coupled to said supply source to be energized therefrom, said ferro-resonant circuit comprising a first and a second winding each for setting up flux in a core of magnetic material and a condenser, said ferro-resonant circuit operating above the jumping point of its characteristic current-voltage curve so that its capacitive reactance is greater than its inductive reactance, and a circuit comprising a portion of said first winding, said condenser, a portion of said second winding and said load, all in series, whereby a substantially constant voltage is impressed across said load.

11. The combination with an alternating-current supply source and a load, of a ferroresonant circuit coupled to said supply source to be energized therefrom, said ierro-resonant circuit comprising a first and a second winding each for setting up flux in a core of magnetic material and a condenser, said ferro-resonant circuit operating above the jumping point of its characteristic current-voltage curve so that its capacitive reactance is greater than its inductive reactance, a second circuit for supplying 10 current fromsaidsourc'efto said first and second windings, and means for supplying current from said source to said load through a circuit comprising said source, said load and a ortion of said first winding, all-in series. 1

1'2. In'combinaticn, a first-anda second winding each for settingiip mm in a core of magnetic material, a condenser, a source of alternatingcurrent, a load, a first circuit comprising in series in the ordernamed said source, saidfirSt winding, said condenser-and 'a'porti'on only of said second winding, .a second circuit comprising in series said source, a 'portion'o'nly of said first winding and a portion only of said second winding,.and.a'thi'rd circuit comprising inseries a portion cm orsaid'nmt winding, sai'd condenser, a portion only of said second winding and said load.

.13. Ac'o'mbina'tion'in accordance with claim 12 in which there 'is p'rovideda 'threerleg'ged core, said first and second windingsbeing wound on different legs, respectively, of said core.

14'. A combination inacco'rdance with claim 12 in" which said first "circuit [is a fierro-resonant circuit "operating above the jumping point of its characteristic current-voltage curve so that said rem-resonant circuit has a capacitivejreactan'ce greater than its inductive reactance.

115. In combination, a firs't winding and a second winding "each for setting up 'fiux in "a core of magnetic material, each of said wind"- ingslhavin'g a first, a'fse'condand'a thirdft'e'rminal, said third 'termina1 being intermediate said "first and second terminals, means for 'cdn'ductive'ly connecting said first terminal of said first winding to said first terminal of said second winding, a condenser, a first current path comprising said condenser connecting said second terminal of said first winding and said second terminal of said second winding, a load, a second current path comprising said load connecting said third terminal of said first winding and said third terminal of said second winding, and means for causing alternating voltages to be set up across said first and second windings and said condenser, respectively, to thereby control the supply of alternating current to said load.

16. A combination in accordance with claim 15 in which said means for causing alternating voltages to be set up across said first and second windings and said condenser, respectively, comprises a third winding magnetically coupled to said first winding, a fourth winding magnetically coupled to said second winding, and means for connecting said third and fourth windings in series to an alternating-current supply source.

17. A combination in accordance with claim 15 in which said means for causing alternating voltages to he set up across said first and second windings and said condenser, respectively, comprises a source of alternating-current, means for connecting one terminal of said source to a terminal of said first winding intermediate said first and second terminals, and means for con necting a, second terminal of said source to a fourth terminal of said second winding, said first and third terminals of said second winding being intermediate said second and fourth terminals thereof.

18. In combination, a first winding means for setting up flux in a core of magnetic material, a second winding means for setting up flux in a core of magnetic material, a condenser, an alternating-current supply source, a load, a ferroresonant circuit coupled to said supply source to be energized therefrom, said term-resonant circuit comprisinga portion at least of each of said first and second winding means and said condenser all in series, said ferro-resonant circuit operating above the jumping point of its current-voltage curve so that its'capacitive reactance is greater than its inductive reactance, a second circuit for supplying current from said source to said first and second winding means, and means for supplying current from said source to said load through a circuit comprising said source, said load and a portion of one at least of said first and second winding means, all in series.

19. In combination, a first and second winding means for setting up fluxes in magnetic circuits, respectively, when current is supplied to said winding means, a condenser, an alternatingcurrent supply source, a load, a first circuit comprising in series said source and a portion of each of said winding means, a second circuit comprising in series said source, said condenser and a portion at least of each of said winding means, said second circuit being a ferro-resonant circuit operating above the jumping point of its characteristic current-voltage curve so that said ferro-resonant circuit has a capacitive reactance which is greater than its inductive reactance, and a third circuit comprising in series said source, a portion of said first winding means and said load, the ampere turns of said first winding means in said second circuit being larger than the ampere turns of said first winding means in said first circuit.

20. In combination, ;a first winding means having a first and a second winding portion each wound on a core of magnetic material, a second winding means having 'a third, a fourth and a fifth winding portion each wound on a core of magnetic material, an alternating-current supply source, a condenser, a load, means for supplying current from said source to said first and third winding portions in series, means for supplying current from" said source to a circuit comprising said second and fourth winding portions and-saidcondenser all in series, said circuit being a series ferro-resonant circuit operating above the jumping point of its characteristic current-voltage curveso thatits capacitive reactance is greater than its inductive reactance, and a circuit comprising said source, said fifth winding portion and saidload all in series, said first and second winding portions producing aiding magnetomotive forces in the core for said firstwinding means, said third and fourth winding portions producing opposing magnetomctive forces in the core for said second winding means.

BRUCE E. STEVENS.

REFERENCES CITED The following references are of record in the file of this patent: 

